The present invention relates generally to electrophoresis, and more particularly to running tank assemblies for electrophoresis.
Electrophoresis is used for a large number of applications. As an example of but one application, DNA sequencing to determine the genetic composition of a sample of DNA can be undertaken using electrophoresis.
Many existing electrophoresis applications are undertaken using so-called running tanks, in which a sample-containing gel is disposed in an electrophoresis chamber in the tank. Electric current is then applied to the gel by means of an electrode in the tank to cause electrophoresis of the sample.
For safety reasons, the electrophoresis chamber preferably is covered by a lid when energized. To ensure that the lid covers the electrophoresis chamber prior to energizing the gel, interlocks have been provided to break the electric current path between an electrophoresis power supply and the tank electrode when the lid is not properly engaged with the running tank.
As one example of such an interlock, microswitches have been provided on the top edge of running tanks, and the microswitches are closed by a lid when the lid is placed on the tank, thereby completing the electrical circuit between the tank electrode and the power supply. Unfortunately, the tank electrode can be energized anytime the microswitches are depressed, whether by a lid or by a substitute mechanism. Thus, the interlock easily can be defeated.
An alternative interlock is disclosed in U.S. Pat. No. 5,405,520, which discloses a plug that is completely recessed into a running tank cover. The cover is formed with a slot that extends to the plug, and a switch on the running tank is advanced into the slot against the plug when the lid is lowered down onto the tank. When the switch contacts the plug, an electrical circuit is established to the running tank electrode. However, the switch can be xe2x80x9cmadexe2x80x9d by contact with components other than the plug in the cover; consequently, the interlock can be easily defeated.
Still another alternate interlock is exemplified in a device marketed under the trade name xe2x80x9cMupid-21xe2x80x9d by Cosmo Bio Ltd. of Japan. In the Mupid-21 device, a running tank cover has a vertical wall and a plug protruding from a front side of the wall. The rear end of the plug is exposed at a rear side of the wall. To engage the lid with a running tank, the lid is lowered onto the tank with the vertical wall of the lid disposed flush against an inside surface of a wall of a power supply bay that is formed as part of the tank. The wall of the power supply bay holds a contact that is connected to the running tank electrode, such that the rear end of the plug wipes the contact when the lid is slid onto the tank. Then, a power supply having a receptacle is advanced into the bay until the plug mates with the receptacle, thereby completing the electrical circuit between the running tank electrode and the power supply.
It happens that a user of an electrophoresis apparatus might undertake many successive electrophoresis experiments over the course of a day, requiring the lid to be removed from the running tank between experiments to modify or replace the gel in the running tank. Unfortunately, the Mupid-21 design necessitates removing the power supply from the bay to remove the lid from the running tank, which users find cumbersome and time consuming. As recognized herein, however, it is possible to provide an electrophoresis running tank assembly which ensures that a power supply cannot be electrically connected to a running tank electrode without first covering the running tank with a lid, and which does not require the power supply to be removed from the assembly to remove the lid from the running tank.
Accordingly, it is an object of the present invention to provide an electrophoresis running tank assembly that addresses one or more of the above-noted problems.
An electrophoresis running tank assembly includes a tank, at least one electrode disposed in the tank, and a lid configured for covering the tank. In accordance with the present invention, the lid includes at least one activation arm protruding from the lid. At least one switch is provided, preferably recessed in a portion of the assembly, and when the lid is engaged with the tank, the activation arm abuts the switch to close the switch and thereby electrically connect the switch to the electrode.
In a preferred embodiment, the switch is held on the tank, and the lid can be lowered onto the tank to a fully lowered position. The activation arm does not close the switch unless the lid is near or in the fully lowered position. In a particularly preferred embodiment, at least two switches and at least two activation arms are provided.
As disclosed in detail below, a power supply holder is associated with the running tank. The power supply holder defines a power supply bay that is configured for removably receiving a power supply. Also, the power supply holder includes a wall and at least one plug extending from the wall into the bay for engaging the power supply when the power supply is disposed in the bay. Additionally, the power supply holder includes a switch enclosure, with the switch being disposed in the switch enclosure and with the activating arm extending into the switch enclosure when the lid is near or in the fully lowered position to thereby activate the switch.
To prevent tilting the lid to gain access to the electrophoresis chamber of the running tank when the arms of the lid are engaged with the switches (and, hence, when the electrodes potentially are energized), the lid is formed with plural skirts that depend down from the edges of the lid and that overlap the sides of the running tank. With this cooperation of structure, tilting of the lid relative to the running tank (and, potentially, access to energized electrodes) is prevented.
In another aspect, an electrophoresis running tank assembly includes a tank defining plural sides that in turn define respective upper edges. At least one electrode is disposed in the tank. Also, a lid is configured for covering the tank. As set forth in detail below, the preferred lid includes at least one activation arm and defines a top plate that rests on the upper edges when the lid is a fully lowered position. Plural skirts depend downwardly from the top plate, with each skirt overlapping a respective side when the lid is near or in the fully, lowered position to prevent tilting of the lid relative to the running tank. When the lid is engaged with the tank, the activation arm abuts a switch to close the switch and thereby electrically connect the switch to the electrode.
In yet another aspect, a method for electrophoresis includes providing a running tank assembly including a running tank with at least one electrode therein. The method also includes engaging a power supply with the running tank assembly and lowering a lid onto the running tank assembly to cover the running tank. Moreover, the method includes causing a switch to close when the lid is lowered onto the running tank assembly to thereby electrically connect the power supply to the electrode. Tilting of the lid relative to the running tank is prevented when the power supply is electrically connected to the electrode.
The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which: